This invention relates to automatic brake controlling devices for a vehicle, such as an automobile.
In automobile automatic brake control systems, there has hitherto been provided an anti-skid controller in which the slip condition of a wheel is detected by comparing output signals proportional to vehicle velocity and wheel velocity obtained from a vehicle velocity detector and a wheel velocity detector, and the vehicle braking system is controlled on the basis of the detection, whereby the wheel is prevented from being locked and inducing a sideslip or a so-called skid by temporarily releasing the brakes.
In such a controller, however, the wheel velocity signal of the wheel velocity detector can reach such an extremely low level that it cannot be detected or it can become ineffective as the wheel begins to stop or during low-speed running of the automobile. In such a case, notwithstanding the fact that the wheel is not actually locked and slipping with respect to the road surface, it is judged incorrectly to be slipping, and the controller operates so as to slacken the brake effect of the braking system. This leads to the disadvantage that the brake does not operate as it should even though it is applied.